Advantages of water over fuel
As we approach those tuning levels we will experience considerable increase in cylinder pressure and temperature, but at the same time more power. Since we cannot raise the melting point of the pistons, we must find a way to control and keep the engine components from overheating. Having six times the latent heat of fuel and huge expansion rate from liquid to gas (single molecule of water - not droplets) water is the ideal substance to inject as a coolant. Having absorbed and dealt with the destructive heat, the by-product (superheated steam at x1400 volume increase) becomes an active partner in adding force to the downward pistons.
Water is converting the extra heat energy for wheel power. Without water, the excessive heat must be transferred to the cooling system and lost into the atmosphere. Since the quantity of water injected is relative small compared to injecting some six times the amount of fuel to arrive at the same cooling property. To all intent and purposes, we are not advising anyone to go this far but the possibility is there and achievable. In most cases, one can venture into the extreme gently. Since water is free, it cost nothing to continue your quest for a highly efficient engine that produce far more power than the fuel dumping method used by the makers.
Fuel octane vs BHP
In turbocharged engines there is a fine balancing act when it comes to making a lot of power on low octane fuel. In most cases, ignition timing must be retarded as the boost pressure rises above a critical point and finally there reaches a further point where the engine simply loses power. If the timing was not retarded with increasing boost, destructive preignition or detonation would occur. Normal combustion is characterized by smooth, even burning of the fuel/air mixture. Detonation is characterized by rapid, uncontrolled temperature and pressure rises more closely akin to an explosion. It's effects are similar to taking a hammer to the top of your pistons.
Most engines make maximum power when peak cylinder pressures are obtained with the crankshaft around 15 degrees after TDC. Experimentation with increasing boost and decreasing timing basically alters where and how much force is produced on the crankshaft. Severely retarded timing causes high exhaust gas temperatures which can lead to preignition and exhaust valve and turbo damage.
We have a hypothetical engine. It's a 2.0L, 4 valve per cylinder, 4 cylinder type with a 9.0 to 1 compression ratio and it's turbocharged. On the dyno, the motor puts out 200hp at 4psi boost with the timing at the stock setting of 35 degrees on 92 octane pump gas with an air/fuel ratio of 14 to 1. We retard the timing to 30 degrees and can now run 7psi and make 225hp before detonation occurs. Now we richen the mixture to 12 to 1 AFR and find we can get 8psi and 235 hp before detonation occurs. The last thing we can consider is to lower the compression ratio to 7 to1. Back on the dyno, we can now run 10psi with 33 degrees of timing with an AFR of 12 to 1 and we get 270 hp on the best pull.
We decide to do a test with our 9 to 1 compression ratio using some 118 octane leaded race gas. The best pull is 490 hp with 35 degrees of timing at 21 psi. On the 7 to 1 engine, we manage 560 hp with 35 degrees of timing at 25psi. To get totally stupid, we fit some larger injectors and remap the EFI system for126 octane methanol. At 30psi we get 700hp with 35 degrees of timing!
While all of these figures are hypothetical, they are very representative of the gains to be had using high octane fuel. Simply by changing fuel we took the 7 to 1 engine from 270 to 700 hp. From all of the changes made, we can deduce the effect certain changes on hp; Retarding the ignition timing allows slightly more boost to be run and gain of 12.5%. Richening the mixture allows slightly more boost to be run for a small hp gain however, past about 11.5 to 1 AFR most engines will start to lose power and even encounter rich misfire. Lowering the compression ratio allows more boost to be run with less retard for a substantial hp gain. Increasing the octane rating of the fuel has a massive effect on maximum obtainable hp. We have seen that there are limits on what can be done running pump gas on an engine with a relatively high compression ratio. High compression engines are therefore poor candidates for high boost pressures on pump fuel. On high octane fuels, the compression ratio becomes relatively unimportant. Ultimate hp levels on high octane fuel are mainly determined by the physical strength of the engine. This was clearly demonstrated in the turbo Formula 1 era of a decade ago where 1.5L engines were producing up to 1100 hp at 60psi on a witches brew of aromatics. Most fully prepared street engines of this displacement would have trouble producing half of this power for a short time, even with many racing parts fitted.
Most factory turbocharged engines rely on a mix of relatively low compression ratios, mild boost and a dose of ignition retard under boost to avoid detonation. Power outputs on these engines are not stellar but these motors can usually be seriously thrashed without damage. Trying to exceed the factory outputs by any appreciable margins without higher octane fuel usually results in some type of engine failure. Remember, the factory spent many millions engineering a reasonable compromise in power, emissions, fuel economy and reliability for the readily available pump fuel. Despite what many people think, they probably don't know as much about this topic as the engineers do.
One last method of increasing power on turbo engines running on low octane fuel is water injection. This method was evaluated scientifically by H. Ricardo in the 1930s on a dyno and showed considerable promise. He was able to double power output on the same fuel with the aid of water injection.
First widespread use of water injection was in WW2 on supercharged and turbocharged aircraft engines for takeoff and emergency power increases. The water was usually mixed with 50% methanol and enough was on hand for 10-20 minutes use. Water/methanol injection was widely used on the mighty turbocompound engines of the '50s and '60s before the advent of the jet engine. In the automotive world, it was used in the '70s and '80s when turbos suddenly became cool again and where EFI and computer controlled ignitions were still a bit crude. Some Formula 1 teams experimented with water injection for qualifying with success until banned. My personal experience with water injection is considerable. I had several turbo cars fitted with it. One 2.2 liter Celica with a Rajay turbo, Weber carb and no intercooler or internal engine mods ran 13.3 at 103 on street rubber on pump gas back in 1987. This was accomplished at 15psi. With the water injection switched off, I could only run about 5 psi before the engine started to ping. I think you might see water injection controlled by microchips, catch on again in the coming years on aftermarket street turbo installations. It works.
Methanol corrosion myth (BUSTED)
Lets put out some strait facts, These are internal combustion engines not parts sitting in a vat of water and methanol. If you soaked a Head in methanol of course it's going to corrode the same thing for a engine block. intake manifold ect.
All of these fluids are in vapor or steam form long before they reach the combustion chambers and hit the boiling points shortly after entering the intake. This is why your intake is ice cold after the water/methanol has gone through it because the change over has removed the heat in the process.
This is a pretty simple fact and concept I'm just wonder why people think it's going to eat pistons, Heads, blocks, intakes. Leaving it in aluminum tanks is not a good ideal as it can cause corrosion as well as metal fuel lines and tubing. Basically immersion is how corrosion happens not bening exposed to methanol vapor and steam.
Here's another simple fact E85 enough said. Its 85% Ethanol
Many motors have come and gone on alcohol injection and have been pulled apart I can't think of one case of internal corrosion of any kind being reported. In fact it's the flip side everyone I have seen looks pretty much spotless in the intake, Heads, and combustion chambers almost no carbon buildup. And ZERO corrosion. I have seen corrosion in cheap intercooler pipes, Intakes and throttle body blade bolts and the bar that hold the blade but that’s about it.
Effects of carbon build up
A properly tuned engine is required for optimal engine performance. Unless the vehicle is tuned to factory specifications,catalyst and emission related problems including catalyst efficiency codes can be triggered.
Today's tune-up no longer simply consists of replacing plugs and checking fluids. Due to tighter engine tolerances and more sophisticated controls, additional work may need to be performed to prevent and correct emission related codes.
How Does Carbon Build-Up Affect Engine Performance?
As the engine operates, carbon deposits may form in places such as the valves, ports, pistons, head gasket and piston rings. This carbon can interfere with normal combustion is several ways. It can alter the engines operating temperature, compression ratio, and several other important factors involved with combustion and sensor readings.
How Can Carbon Alter the Sensor Readings?
The carbon contributes to abnormal combustion in several ways, but the most dramatic effect in a modern fuel injected engine is the "sponge effect". As the fuel mixture in the cylinder is compressed, the carbon has a tendency to absorb both oxygen and fuel. Once the ignition spark fires, the flame front normally spreads through the chamber, consuming the fuel and air, however, the carbon has a tendency to extinguish the flame front and stifle combustion.
This, combined with the fuel and air that was absorbed, results in poor efficiency. As the chamber decompresses during the exhaust portion of the stroke, the unburned fuel and air is released, resulting in both excessive fuel and air (containing oxygen) entering the exhaust system. The O2 sensor detects the excessive oxygen and the vehicle computer (ECM, ECU, PCM) compensates for this by enriching the mixture.
This causes poor catalyst efficiency, and increased carbon formation. The situation is aggravated by the overly rich mixture, resulting in the engine's failure to reach a sufficient temperature to remove these deposits. In addition, the excess fuel can permanently damage the catalyst or cause meltdown (on the outlet side as opposed to the inlet) and can get hot enough to melt stainless steel substrates.
Does Carbon Alter Combustion in Other Ways?
Absolutely, in addition to causing poor combustion, excessive build up can also alter the vehicle's compression ratio. The carbon fills up spaces around the piston rings, head gasket, and spark plugs. This decreases the amount of space that is available in the combustion chamber. This increases the compression, which can cause the engine to overheat, ping (detonate), and also causes an increase in NOX emissions. Due to the fact that the carbon can retain oxygen from the combustion process, it can cause another interesting effect that can cause the vehicle to either trigger a light or fail an emissions test.
A catalytic converter requires certain conditions to break down harmful emissions. It requires a slightly rich mixture and a low oxygen level in the exhaust system to break down NOX. Because the carbon causes increased NOX emissions and also causes excessive oxygen to leave the combustion chamber unconsumed, this actually impairs the catalyst's ability to remove the NOX from the exhaust.
Now people running alcohol injection don't have to worry about any of the above
This topic has often been mentioned in internal combustion engine publications and many SAE papers (Society of Automotive Engineering). I will do my best to explain what it is and how it can be implemented in automotive engines constructively. Please notify me of any mistakes or inaccuracies made so that I can correct them.
Unlike any other liquid, water has the highest latent heat of vaporisation of all the known liquids that exist on this planet, naturally other than Mercury. Its strong inter-molecular bond is the main reason why it requires a large amount of heat energy to separate its molecules from each other. It requires 2240KJ of heat energy to fully vaporise one litre of liquid water into gas. Translating this into meaningful terms, a 3KW domestic electrical kettle will need 12 minutes or so to fully evaporate one litre of water, the equivalent energy to keep a 100W light bulb on for 6 hours.
A contardiction in terms?
You are now probably wondering why we are injecting water into any engine resulting only in taking heat energy (power) away since the sole purpose of a car engine is to convert air and fuel into heat energy to do the work of turning the wheels. Let us first look at the thermal dynamics of an engine - the energy produces is basically shared amongst three areas, pretty equally. One third is lost in the exhaust pipe; one third is transferred into the atmosphere via the normal cooling system. The remainder is for turning the wheels. As this document progresses, the reason for adding water injection will become more apparent.
Aiming for a highly efficient and powerful engine set up:
Having covered the engine basics, we can now examine how one can improve the efficiency of an engine by recovering some of the heat loss mentioned above. Engine efficiency can be greatly improved by increasing the compression ratio - the ratio that governs how much of the energy is channelled into useful power rather than just plain heat loss to the atmosphere. A normal spark ignition engine runs at an average compression ratio of between 9:1 to 10:1. The limitation here is the octane rating of fuel used, the higher the octane number the higher the compression ratio that can be used. In other words, an engine designed to run on 98-octane fuel will be more efficient and potentially produces more power than an engine designed to run on lower octane fuel. Octane rating is a measure of knock resistance - a higher knock resistance will allow an engine to run a higher compression ratio or more ignition advance hence producing more power.
How manufacturers contribute towards it:
Modern electronics has played a big part in allowing a normally aspirated engine to run a vast range of fuel grades by constantly adjusting the ignition timing until the knock limit is a degree or two ahead. Your engine is now getting the optimum timing ( by varying the effective compression ratio with the ignition trim) for a given grade of fuel. In order to stretch the efficiency of engine further with a given amount of air it can inhale, a turbocharger is added. The heated gas from the exhaust is harvested to power an air pump (compressor) to improve the volumetric efficiency of the engine. This arrangement will recover some of the wasted energy towards the wheels instead of being lost to the atmosphere.
Nowadays, modern electronics can further improve the power output of a Turbocharged engine by constantly modifying the boost pressure. Although a turbocharger can stretch the dynamic operation range of an ordinary engine it is still somewhat limited by the fuel grade used - over stepping this limit will result in the onset of detonation.
Stretching the limits on a Turbocharged engine
The easiest way to extract more power output is by increasing the octane rating of the fuel (race fuel has that property). Any race fuel will allow you to run extra boost and extra timing thus further improving the efficiency of an engine. Unfortunately race fuel is not easily obtainable from normal commercial petrol stations. An intercooler will further improve the efficiency of a turbocharger by increasing the density of the compressed air from the turbocharger.
Extending the limit further.
So far we have outlined some existing methods to push the barrier further and most of the mentioned methods have already been implemented on some modern turbocharged engines. So how can the injection of water squeeze more efficiency out of a modern engine? The answer is - you can't, unless you are prepared to increase the existing compression ratio further. In the case of a turbocharged engine, it means running a higher pressure-ratio. This is not new, car manufacturers are already using this technique such as timed over-boost during acceleration and boost tapering down over certain RPM etc. During these periods, the a/f mixture is enriched to assist in-cylinder cooling.
Power comes with a price.
With every modern factory turbo car produced nowadays, it is fuel-efficient until pressed hard. I have not seen any factory equipped turbo cars that doesn't dump fuel under hard acceleration. It is not the preferred intention of the makers but they have little choice, since they have no other means to control the thermal loading within the combustion chamber. A bigger radiator or oil cooler is one answer however unfortunately the frontal area of the car doesn't increase with the power output of the car.
How Water Injection can take you past the final barrier
We have finally arrived at the main topic - water injection. So far we are seeking a way to improve the efficiency of the engine and hence how much power can be squeezed out of an existing set up and of course without using extra fuel - we call it the final barrier. We will address this particular area of the turboed engine's dynamics and sum up how water injection can contribute in different areas and the reasoning behind the claim.
Water Injection will improve the turbo operating range:
A turbocharger has a designed operating range defined by a chart. Its flow characteristics are selected carefully to match the engines operating characteristics by car makers. Each operation range has an efficiency boundary denoted by percentage. Ideally, one should operate within the most efficient boundary area. When boost is increased, it tends to shift the operating range outside this area. Loosing about 5% efficiency each time it is shifted further away from the ideal boundary. It doesn't mean that it stops working altogether but the loss in efficiency almost always translated into heat. The further away the shift, the hotter the charge the air gets. Almost all modern turbo cars use intercoolers to reduce those high charge air temperatures.
Introducing water injection will absorb any heat left over from the factory's intercooler designed capacity when the turbocharger's operating range is extended. High ambient and low vehicle speed will further tax the efficiency of the intercooler so having a water injection as a secondary cooling mechanism is very useful. Water does not have the problem absorbing heat as the intercooler in less-than-ideal conditions. Provided the water is well atomised and exhibits a great deal of surface area, it will grab heat very quickly. As the cooling effect is taking place, the air shrinks to accommodate more air coming out of the turbo or intercooler, resulting a extra throughput of charge air. The myth of water vapour displacing the air is sometimes over-stated - the volume of the water vapour occupied is minimal. It has to be noted that when the temperature in the inlet drops, the droplet size decreases and occupied less air space.
Water droplets working hard in the combustion chamber.
We have now arrived at the most important aspect of water injection in dealing with overall performance gain and fuel efficiency. Moistened air has the effect of reducing the temperatures of the surrounding engine components as it enters the combustion chamber allowing better volumetric efficiency of the induction stroke. Some cooling capacity is used during this cycle so the droplet size becomes smaller but only to the advantage of the next engine cycle. During the compression stroke, tiny water droplets are distributed amongst the charge air in the ratio of about 120:1 (based on water to fuel ratio of 10:1). This has the effect of regulating the flame speed thus promoting even flame propagation speed. The predicable burnt rate is essential for accurate ignition mapping to produce consistent power.
Any non-homogeneous a/f mixture exhibits abrupt frame-front temperature changes, this condition promotes the onset of detonation especially towards the end burnt period. Once detonation has started, it will tend to continue for the next few cycles even the subsequent condition is normal. The most common solution adopted by most engine management to avoid this from happening is by running an over-rich mixture. This has two effects - excess fuel cools the mixture and slows down the burnt rate. Slowing down the frame speed has the effect of shifting the peak cylinder pressure curve during the power stroke. When pressure is build up further away from the top dead centre (TDC) line it will minimise the onset of detonation but in expense of loosing some pressure that feeds the pistons to tuning the wheels. Rich mixture not only wastes fuel but it forms carbon monoxide molecules, a product that has only 30% energy release of the carbon dioxide, a fully oxidised carbon molecule. Every molecule of carbon monoxide carries an oxygen molecule out of your exhaust. Keep in mind that the engine only inhales about 20% of oxygen and should be treasured.
Now comes to the all-important reason why we are injecting water to rob heat energy - in order to push the power boundary further to obtain some meaningful figures, the boost pressure can be increased further (higher effective compression), aim towards MBT (maximum brake torque) timing and 12.5:1 a/f ratio. Since the use of race fuel is not on the menu. As we approach those tuning levels we will experience considerable increase in cylinder pressure and temperature, but at the same time more power. Since we cannot raise the melting point of the pistons, we must find a way to control and keep the engine components from overheating. Having six times the latent heat of fuel and huge expansion rate from liquid to gas (single molecule of water - not droplets) water is the ideal substance to inject as a coolant.Having absorbed and dealt with the destructive heat, the by-product (superheated steam at x1400 volume increase) becomes an active partner in adding force to the downward pistons. Water is converting the extra heat energy for wheel power. Without water, the excessive heat must be transferred to the cooling system and lost into the atmosphere. Since the quantity of water injected is relative small compared to injecting some six times the amount of fuel to arrive at the same cooling property. To all intent and purposes, we are not advising anyone to go this far but the possibility is there and achievable. In most cases, one can venture into the extreme gently. Since water in free, it cost nothing to continue your quest for a highly efficient engine that produce far more power than the fuel dumping method used by the makers.
One word of warning, a water injection with good failsafe capabilities must be your first priority when you are choosing one. So how much water should be injected to be effective? For those how want to extract the maximum power and not achieving maximum economy. To date, apart from the Audi FSI and some new Honda engines, it is considered an a/f ratio of 12:5:1 a/f ratio will yield maximum power and 14.5:1 for maximum economy. The exact a/f ratio vary from engine to engine, it has a great deal to do with how homogeneous is the mixture induced. We know that under WOT, full boost conditions most turbo car’s a/f ratio drops down to 10:1 to 10:5:1. 3% water to fuel will be have the same heat-absorption properly of the excess-fuel as running from 12.5:1 to 10.1:1 a/f ratio. We normally recommend 10% of water top fuel to make it extra safe.